(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of forming uniform ultrathin silicide features in the fabrication of integrated circuits.
(2) Description of the Prior Art
In the fabrication of integrated circuits, the fabrication of ultrathin uniform silicide layers on sub 0.1 micron features is expected to be extremely difficult using the standard salicide (self-aligned silicide) process. A key problem is the interfacial non-uniformity as the silicide thickness is scaled down from about 1000 Angstroms to about 300 Angstroms. This non-uniformity issue of. ultrathin silicide films is mainly related to the statistical nature of the nucleation events required to form the resulting low-resistivity phase, as well as the non-uniformity of the existing rapid thermal annealing (RTA) process.
U. S. Pat. No. 5,712,191 to Nakajima et al teaches spin coating a nickel acetate solution onto a silicon layer and heat treating at 300-500.degree. C. to form nickel suicide. A laser light is then irradiated to promote crystal growth in the area of the nickel silicide. However, laser irradiation or modification may not allow features smaller than submicron scale to be fabricated. Laser irradiation only allows a single localized modification at any one time. Additionally, laser irradiation has been observed experimentally to induce cracks and film peelings due to the large thermal shock induced in the localized nickel oxide regions at any one time within an extremely short time period. U.S. Pat. No. 5,510,295 to Cabral, Jr. et al teaches depositing a cobalt layer over silicon, annealing the cobalt layer at 900-1000.degree. C. in a N.sub.2 ambient, then depositing a titanium layer thereover and annealing to form titanium silicide. U.S. Pat. No. 4,908,334 to Zuhr et al forms a silicide film by ion beam deposition of metal onto silicon at 400-600.degree. C. U.S. Pat. No. 5,728,625 to Tung discloses growing cobalt silicide on silicon in ultra-high vacuum and growing cobalt on silicon and then annealing at 450-800.degree. C. to form cobalt silicide. U.S. Pat. No. 5,702,972 to Tsai et al teaches depositing titanium onto silicide to form titanium silicide and then annealing to change the titanium silicide from phase C49 to phase C54. U.S. Pat. No. 4,957,777 to Ilderem et al teaches depositing titanium silicide over polysilicon using silane.